Sensitive midges fly on two wings and a prayer

ANOTHER LIFE:IT'S WEEKS SINCE the swallows were here, dashing up and down between house and gate, over and over, figures-of-eight, amazing G-turns between the trees: they knew where the midges were. And now neither midges nor swallows, but delicious early-morning walks without a lick of protective citronella.

But that’s nothing. An even keener observer of nature, living in west Cork, has been river- fishing for sea trout three or four nights a week in the Bandon and Ardigeen valleys. In other years this meant smothering himself with midge cream, but this summer, he says, there haven’t been any, even on damp, muggy evenings. Even the bats that live under the bridge have been whisking off to hunt somewhere else. And he can go on gardening until dusk without protection – a boon unknown in 35 years at the humid end of the county.

Casting his trout fly into the dark, and brooding on the mystery, our fisherman’s relief from bites has been soured with worry and foreboding: could it be that mobile phone masts, he wondered, are disorienting insects – not just midges, but bees and other beneficial creatures on the wing? This truly appalling thought he shared with his mates on IBN-L, the birders’ network.

In these increasingly unnatural times, it’s natural to seek in human doings the causes of phenomena that seem to come perilously close to the things we don’t know we don’t know. But the idea of such disruptive electromagnetic waves brought a circumspect response from a birding scientist in Queen’s University: “I think it might be extremely difficult to prove, or even demonstrate, a link between the magnetic fields generated by the masts and demise of flies by disorientation.”

Beyond moths, infrared waves and candle-flames, I don’t know enough about the invisible world impinging on insect antennae to take the proposal further. But this spring did bring some new science to bear on dramatic fluctuations in midge numbers, described in a paper in the science journal Nature: “High-amplitude fluctuations and alternative dynamical states of midges in Lake Myvatn.”

This great and scenic lake in Iceland is, as many travellers will know, one of the midgiest places on earth – indeed, Midge Lake is what Myvatn means. It also attracts birding tourists in particular, having the widest range of waterfowl in the world. Like the lake’s population of Arctic char, the birds feed on the midges, but these can go through million-fold swings of abundance. In some years there are scarcely any; in others, as Dr Árni Einarsson of the University of Iceand, says, “you have to fight not to inhale them”. (Fortunately, Tanytarsus gracilentus is not a biting species.)

Dr Einarsson was one of a team of ecologists studying this erratic abundance. Their mathematical modelling showed that the changes in midge numbers flip between two patterns: a more-or-less constant population over several years, or cycles of repeated boom-and-bust. In the last 40 years, however, the fluctuations have become more extreme and, in seasons of midge crashes, the lake’s Arctic char have run out of food – the traditional fishery collapsed in the 1980s – and waterbird reproduction has fallen.

Midge larvae feed on single-celled algae, and the distribution of these had been disturbed by dredging operations in one basin of Myvatn.

But the lasting lesson from the study was twofold: “Not only are midge dynamics inherently unpredictable, they may also be extremely and unexpectedly vulnerable to small disturbances. . .”

Anything new that can be learned about midge behaviour has become urgently relevant, given the risk of bluetongue virus, widespread among livestock in continental Europe, and lately extended to the United Kingdom. So far, the virus has been carried through the bites of a southern species of midge, Culicoides imicula, but Ireland’s 29 types of midge include other such biters (all females seeking a blood meal to help in egg-laying), notably Culicoides impunctatus, the bane of damp western summers.

A three-year study of midge genetics and habitats has now been launched by NUI Galway’s zoology department. Farmers are also being advised on how to protect their livestock. A bluetongue outbreak in Ireland might well prompt vaccination but, meanwhile, suggestions range from getting sheep and cattle indoors behind mesh-screened doors and windows at least an hour before sunset, to covering dung heaps with plastic and using insect-repellent dips or sprays. Nothing, I notice, in the official advice, about the propane-powered “midge-eating” machines now on the market for several years.

They attract the females from up to 100m around, first with a whiff of carbon dioxide, then, at closer quarters, with synthesised mammal-breath chemicals, finally sucking them into a net where they dehydrate and die.

With the promise of eliminating up to 200,000 female midges per day, hundreds of such machines have been sold in Ireland at around €1,100 each, to country hotels, golf clubs and so on. But not that many, surely, to farmers in the valleys of West Cork?